Process of making a lithographic structure using antireflective materials

ABSTRACT

A lithographic structure comprising: an organic antireflective material disposed on a substrate; and a silicon antireflective material disposed on the organic antireflective material. The silicon antireflective material comprises a crosslinked polymer with a SiO x  backbone, a chromophore, and a transparent organic group that is substantially transparent to 193 nm or 157 nm radiation. In combination, the organic antireflective material and the silicon antireflective material provide an antireflective material suitable for deep ultraviolet lithography. The invention is also directed to a process of making the lithographic structure.

FIELD OF INVENTION

The invention relates to a process of making a lithographic structureusing antireflective materials. In particular, the invention relates toa process of making a lithographic structure using a siliconantireflective material and an organic antireflective material.

BACKGROUND OF THE INVENTION

In the process of making semiconductor devices a photoresist and anantireflective material are applied to a substrate. Photoresists arephotosensitive films used to transfer an image to a substrate. Aphotoresist is formed on a substrate and then exposed to a radiationsource through a photomask (reticle). Exposure to the radiation providesa photochemical transformation of the photoresist, thus transferring thepattern of the photomask to the photoresist. The photoresist is thendeveloped to provide a relief image that permits selective processing ofthe substrate.

Photoresists are typically used in the manufacture of semiconductors tocreate features such as vias, trenches or combination of the two, in adielectric material. In such a process, the reflection of radiationduring exposure of the photoresist can limit the resolution of the imagepatterned in the photoresist due to reflections from the materialbeneath the photoresist. Reflection of radiation from thesubstrate/photoresist interface can also produce variations in theradiation intensity during exposure, resulting in non-uniformlinewidths. Reflections also result in unwanted scattering of radiationexposing regions of the photoresist not intended, which again results inlinewidth variation. The amount of scattering and reflection will varyfrom one region of the substrate to another resulting in furthernon-uniform linewidths.

With recent trends towards high-density semiconductor devices, there isa movement in the industry to use low wavelength radiation sources intothe deep ultraviolet (DUV) light (300 nm or less) for imaging aphotoresist, e.g., KrF excimer laser light (248 nm), ArF excimer laserlight (193 nm), electron beams and soft x-rays. However, the use of lowwavelength radiation often results in increased reflections from theupper resist surface as well as the surface of the underlying substrate.

Substrate reflections at ultraviolet and deep ultraviolet wavelengthsare notorious for producing standing wave effects and resist notchingwhich severely limit critical dimension (CD) control. Notching resultsfrom substrate topography and non-uniform substrate reflectivity whichcauses local variations in exposure energy on the resist. Standing wavesare thin film interference or periodic variations of light intensitythrough the resist thickness. These light variations are introducedbecause planarization of the resist presents a different thicknessthrough the underlying topography. Thin film interference plays adominant role in CD control of single material photoresist processes,causing large changes in the effective exposure dose due to a tinychange in the optical phase. Thin film interference effects aredescribed in “Optimization of optical properties of resist processes”(T. Brunner, SPIE 10 Proceedings Vol. 1466, 1991, 297).

Bottom anti-reflective coatings (BARCs) have been used with singlematerial resist systems to reduce thin film interference with somesuccess. However, BARCs do not provide control of topographic variationsand do not address the differences in resist thickness. BARCs such assilicon nitride or silicon oxide typically follow the already existingtopography, and thus, the BARC exhibits nearly the same thicknessnon-uniformity as the underlying material. Consequently, the BARC alonewill generally not planarize topographic variations resulting fromunderlying device features. As a result, there will be a variation inexposure energy over the resist. Current trends to provide uniformtopography via chemical/mechanical polishing still leaves significantvariations in film thickness.

Variations in substrate topography also limits resolution and can affectthe uniformity of photoresist development because the impingingradiation scatters or reflects in uncontrollable directions. Assubstrate topography becomes more complex with more complex circuitdesigns, the effects of reflected radiation becomes even more critical.For example, metal interconnects used on many microelectronic substratesare particularly problematic due to their topography and regions of highreflectivity.

One approach to variations in substrate topography is described in U.S.Pat. No. 4,557,797 (Fuller et al.). Another approach used to addressvariations in substrate topography is described in Adams et al.,Planarizing AR for DUV Lithography, Microlithography 1999: Advances inResist Technology and Processing XVI, Proceedings of SPIE, vol. 3678,part 2, pp 849-856, 1999, which discloses the use of a planarizingantireflective coating.

Although multimaterial patterning schemes exist in the prior art (see,U.S. Pat. No. 6,140,226; and R. D. Goldblett, et al. Proceedings of theIEEE 2000 International Technology Conference, p 261-263), there remainsthe need for new antireflective materials. Many of the priorantireflective materials contain silicon based intermediate materialsthat do not act as antireflective coatings, e.g. silicon oxide likematerials require the use of an additional antireflective coatingbecause they cannot be optically tuned to control reflections.

The present trend to 248 nm and 193 nm lithography and the demand forsub 200 nm features requires that new processing schemes be developed.To accomplish this, tools with higher numerical aperture (NA) areemerging. The higher NA allows for improved resolution but reduces thedepth of focus of aerial images projected onto the resist. Because ofthe reduced depth of focus, a thinner resist is typically required.However, as the thickness of the resist is decreased, the resist becomesless effective as a mask for subsequent dry etch image transfer to theunderlying substrate. Without significant improvement in the etchresistance exhibited by current single material resists, these systemscannot provide the necessary etch characteristics for high resolutionlithography.

SUMMARY OF THE INVENTION

The invention is directed to a lithographic structure comprising: anorganic antireflective material disposed on a substrate; and a siliconantireflective material disposed on the organic antireflective material.The silicon antireflective material comprises a crosslinked polymer witha SiO_(x) backbone, a chromophore, and a transparent organic group thatis substantially transparent to 193 nm or 157 nm radiation. In manyinstances, the silicon antireflective material will further comprise areaction product resulting from the reaction of a thermal acidgenerator.

In combination, the organic antireflective material and the siliconantireflective material provide an antireflective material suitable fordeep ultraviolet lithography. The lithographic structure is then used topattern a substrate. The invention is also directed to a process ofmaking a lithographic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood by reference to the DetailedDescription of the Invention when taken together with the attacheddrawings, wherein:

FIG. 1 is a simulated plot of reflectivity for an antireflectivematerial in the art and for a silicon antireflective material disposedon an organic antireflective material according to the invention; and

FIG. 2 is a schematic representation for the patterning of a substrateaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

To address many of the lithographic processing issues summarized in the“Background of the Invention”, applicants have developed a lithographicstructure that includes a silicon antireflective material in combinationwith an organic antireflective material. The use of two antireflectivematerials provides the engineer with the process control and flexibilityrequired for high resolution (low wavelength) lithography. For example,the engineer can selectively etch the organic antireflective materialrelative to the silicon antireflective material. As a result, once thesilicon antireflective material is patterned, the underlying organicantireflective material can be etched with minimal removal of thesilicon antireflective material.

For many lithographic imaging processes, the resists used do not providesufficient resistance to subsequent etching steps to enable effectivetransfer of the resist pattern to a material underlying the resist. Theresist typically gets consumed after transferring the pattern into theunderlying BARC and substrates. In addition, the trend to smaller sub 90nm node feature sizes requires the use of an ultra thin resist (>200 nm)to avoid image collapse. In many instances, if a substantial etchingdepth is required, or if it is desired to use certain etchants for agiven underlying material, the resist thickness is now insufficient tocomplete the etch process.

Applicants' lithographic structure and process addresses many of theabove issues by initially transferring the pattern onto a siliconantireflective material which then serves as an etch mask to continuetransferring the pattern into a relatively thick organic antireflectivematerial.

The invention also provides the process engineer with the opticaltunability or flexibility to control the antireflective properties ofthe lithographic structure, if needed. Through the specific selection ofsilicon and organic antireflective materials a lithographic structurewith the desired optical characteristics for high resolution, deepultraviolet imaging is possible. Proper selection of optical constantsfor the silicon and organic antireflective materials can suppress theundesired reflectivity from the polarization nodes TE and TM (x and ypolarization states) at high NA lithography.

The invention is directed to a lithographic structure comprising: anorganic antireflective material disposed on a substrate; and a siliconantireflective material disposed on the organic antireflective material.The silicon antireflective material comprises a crosslinked polymer witha SiO_(x) backbone and a chromophore attached to the SiO_(x) backbone.The crosslinked, silicon oxide polymer also includes a transparentorganic group that is substantially transparent to 193 nm or 157 nmradiation. In many instances, the silicon antireflective material willfurther comprise a reaction product resulting from the reaction of athermal acid generator. The lithographic structures provides the neededoptical and mechanical properties as well as etch selectivity.

The polymer is crosslinked through reactive sites on the polymer with anexternal crosslinking agent. Typically, the reactive site is afunctional group, e.g., hydroxyl, on the chromophore or the organictransparent group. Alternatively, the polymer can include internalcrosslinking groups, i.e., attached to one of the organic groups of thepolymer, e.g., the chromophore or the organic transparent group.

The organic antireflective material is a crosslinked polymer withlittle, if any, silicon. The organic antireflective material can beformed by spin coating followed by crosslinking. Organic antireflectivematerials and the processes by which they are made are well known tothose in the art of semiconductor processing.

The silicon antireflective material is optically tuned by carefulselection of the chromophore, or the organic transparent group of thepolymer. The degree of oxygen in the SiO_(x) polymer also can be used tooptically tune the silicon antireflective material. In addition, theselection of an organic antireflective material with the appropriateoptical constants in combination with a selected silicon antireflectivematerial can provide a semiconductor structure with excellentantireflective properties at 193 nm radiation, in particular at high NAlithography.

The silicon oxide polymer used to form the silicon antireflectivematerial is preferably an organosiloxane, more preferably anorganosilsesquioxane. Examples of suitable silicon oxide polymers of thesilsesquioxane-type (ladder or network) have structures I to III below:

where R₁ comprises a chromophore, R² comprises an organic grouptransparent to 193 nm radiation, and R³ comprises a reactive siteavailable for crosslinking.

Examples of suitable silicon oxide polymers of the organosiloxane-typehave structures IV to VI below:

where R¹, R² and R³ are as described above. The silicon oxide polymercan also contain various combinations of structures I to VI such thatthe average silicon oxide structure with a chromophore R¹ is representedas structure (VII) below and the average structure with a reactive siteR² is represented by structure (VIII) below, and the average structurewith a reactive site R³ is represented by structure (IX) below.

where x is from about 1 to about 1.5.

The silsesquioxane-type polymers (I to III) will often have superioretch resistance. Still, if the organosiloxane-type polymers are used (IVto VI), the degree of crosslinking is generally increased compared toformulations based on silsesquioxanes. In many cases, the silicon oxidepolymer will have solution and film-forming characteristics conducive toforming a layered material by conventional spin-coating.

Exemplary silicon oxide polymer compositions used to provide the siliconantireflective material of the invention and methods of depositing sucha material is described in U.S. Pat. Nos. 6,420,088 and 6,730,454,assigned to International Business Machines, the entire disclosures ofwhich are incorporated herein by reference. A select listing of siliconoxide polymers that can be used are lisyed on column 4, line 45 tocolumn 5 line 8 of U.S. Pat. No. 6,420,088.

Alternatively, the polymer compositions described in Japanese patentapplication 2004-158639, Japanese patent application 2003-157808 orJapanese patent application 2004-172222, the entire disclosures of whichare incorporated herein by reference, can be used to provide the siliconantireflective material of the invention.

The following silicon oxide polymer depicted below provides a siliconantireflective material with optimal characteristics and performance.

The chromophore-containing groups R¹ may contain any suitablechromophore which (i) can be grafted onto the silicon polymer (ii) hassuitable radiation absorption characteristics, and (iii) does notadversely affect the performance of the material or any overlyingphotoresist material. Preferred chromophore moieties include chrysenes,pyrenes, fluoranthrenes, anthrones, benzophenones, thioxanthones, andanthracenes. Anthracene derivatives, such as those described in U.S.Pat. No. 4,371,605 can also be used. The chromophore 9-anthracenemethanol is a preferred chromophore for 248 nm lithography.

Other chromophores suitable for this invention are described in U.S.Pat. No. 6,730,454; Japanese patent application 2004-158639; andJapanese patent application 2004-172222, the disclosures of which isincorporated herein by reference. An exemplary list include chromophoresselected from the group consisting of phenyl, phenol, naphthalene, andan unsaturated organic group. The use of a phenyl chromophore for 193 nmlithography exhibits certain advantages over some of the otherchromophores listed. Also, for 193 nm lithography, non-aromaticcompounds with one or more unsaturated carbon-carbon bonds can be used.

The chromophore can be chemically attached to the silicon polymer byacid-catalyzed O-alkylation or C-alkylation such as by Friedel-Craftsalkylation. Alternatively, the chromophore can be chemically attached byesterification. For example, the chromophore can be attached via ahydroxyl-substituted aromatic group such as a hydroxybenzyl orhydroxymethylbenzyl group.

The selection of the transparent organic groups R² used will depend onthe wavelength or character of the imaging radiation. In the case of 193nm imaging radiation, the transparent organic groups are preferablybulky (C₂ or higher) organic radicals substantially free of unsaturatedcarbon-carbon bands. Organic transparent groups such as epoxides areparticularly suited for 193 nm lithography. A cycloaliphatic epoxideexhibits exceptional characteristics for 193 nm lithography. Otherfunctional groups such as an alcohol, acetoxy, ester and/or ether basedtransparent groups can also be used.

Organic transparent groups that can be used in the siliconantireflective materials are described in U.S. Pat. No. 6,730,454;Japanese patent application 2004-158639; and Japanese patent application2004-172222. In many instances, the amount of transparent organic groupsis preferably balanced with the amount of chromophore to provide adesired combination of energy absorption and antireflection character inthe silicon antireflective material.

In the case of 157 nm imaging radiation, the organic transparent groupsare preferably fluorine-containing groups such as a trifluoromethylgroup or a perfluoroalkyl. Again, the amount of transparent organicgroups is preferably balanced with the amount of chromophore to providea desired combination of energy absorption and antireflection characterin the silicon antireflective material.

The reactive site R³ comprises alcohols, more preferably aromaticalcohols (e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) orcycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclicalcohols such as fluorocarbon alcohols, aliphatic alcohols, aminogroups, vinyl ethers, and epoxides can be used.

The external crosslinking agent used to form the silicon antireflectivematerial can be one that reacts with the silicon polymer and iscatalyzed by an acid and/or by heat. Generally, the crosslinking agentcan be any suitable crosslinking agent known in the negative photoresistart which is otherwise compatible with the other selected components ofthe polymer composition. Preferred crosslinking agents are glycolurilcompounds such as tetramethoxymethyl glycoluril,methylpropyltetramethoxymethyl glycoluril, andmethylphenyltetramethoxymethyl glycoluril, available as POWDERLINK® fromCytec Industries.

Other possible crosslinking agents include:2,6-bis(hydroxymethyl)-p-cresol compounds such as those found inJapanese Laid-Open Patent Application (Kokai) No. 1-293339, etherifiedamino resins, for example methylated or butylated melamine resins(N-methoxymethyl- or N-butoxymethyl-melamine respectively), andmethylated/butylated glycolurils, as can be found in Canadian Patent No.1 204 547. Other crosslinking agents such as bis-epoxies or bis-phenols(e.g., bisphenol-A) can also be used. Combinations of two or morecrosslinking agents can also be used.

The following crosslinker depicted below provides a siliconantireflective material with optimal characteristics and performance.

The silicon oxide polymer compositions used to form the siliconantireflective material will likely contain an acid generator, which isused to catalyze the crosslinking of the polymer. The acid generator canbe a compound that liberates acid upon thermal treatment. A listing ofknown thermal acid generators include2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyltosylate and other alkyl esters of organic sulfonic acids. Compoundsthat generate a sulfonic acid upon activation are generally suitable.Other suitable thermally activated, acid generators are described inU.S. Pat. Nos. 5,886,102 and 5,939,236; the disclosures of these twopatents as related to the thermally activated, acid generating compoundsare incorporated herein by reference.

If desired, a radiation-sensitive acid generator can be used as analternative to a thermally activated acid generator or in combinationwith a thermally activated acid generator. Examples of suitableradiation-sensitive acid generators are described in U.S. Pat. Nos.5,886,102 and 5,939,236, the disclosures of these two patents as relatedto radiation sensitive, acid generating compounds are incorporatedherein by reference. Other radiation-sensitive acid generators known inthe resist art can be used as long as they are compatible with the othercomponents of the polymer composition.

The following acid generator depicted below provides a siliconantireflective material with optimal characteristics and performance.

wherein A is S or I, and x is 0 to 7.

The silicon oxide polymer compositions can contain (on a solids basis)(i) about 50-98 wt. % of the silicon polymer, more preferably about70-80 wt. %, (ii) about 1-50 wt. % of crosslinking agent, morepreferably about 3-25% wt. %, and (iii) about 1-20 wt. % acid generator,more preferably about 1-15 wt. %.

The silicon oxide polymer compositions will generally contain a solvent.The solvent may be any solvent conventionally used with resists whichotherwise does not have any excessively adverse impact on theperformance of the antireflective composition. Exemplary solventsinclude propylene glycol monomethyl ether acetate, cyclohexanone, andethyl lactate. The compositions can also contain small amounts ofauxiliary components (e.g., base additives, etc.) known in the art.

The silicon oxide polymer compositions can be prepared by combining thesilicon oxide polymer, crosslinking component and acid generator, andany other desired ingredients (e.g., solvent) using conventionalmethods. The silicon polymer compositions can be deposited on theorganic antireflective material by spin-coating followed by heating toachieve crosslinking and solvent removal. The heating is preferablyconducted at about 250° C. or less, more preferably about 150° C. to220° C. The heating time will depend on the material thickness andtemperature.

The organic antireflective material used in the lithographic structurecan be any polymer containing the elements of carbon, hydrogen, oxygenand nitrogen and mixtures thereof, that can be spin applied andcrosslinked with a heat treatment. Typical organic polymer compositionssuitable for this invention are being used in lithographic applicationssuch as organic BARCs or as planarizing undermaterials in bimaterial orother multimaterial lithographic schemes. The choice of the appropriateorganic polymer composition will depend upon the optical constants asdescribed in the section below. Examples of suitable organic polymercompositions are described in U.S. Pat. Nos. 6,503,689; 6,410,209;6,686,124; and U.S. published application 20020058204A1, the entiredisclosures of which are incorporated herein by reference.

The selection of which organic antireflective polymer composition to usewill depend on several characteristics such as solubility, opticalproperties, thermal properties, mechanical properties, etch selectivity,and film forming ability. The resulting organic antireflective materialwill be suitable for low-wavelength radiation. Like the silicon oxidepolymer described above, the organic polymer can have a plurality ofdifferent chemical groups each having a specific function in the overallperformance of the material. Optical properties, mode ofinsolubilization, solubility enhancement, and etch resistance are amongthe properties that can be tailored by a judicious selection of thechemical groups.

Examples of suitable organic polymers that can be used includepoly(4-hydroxystyrene), copolymers of 4-hydroxystyrene such as with upto 40 weight % of an alkyl methacrylate, alkylacrylate and/or styrene;novolac resins, acrylate polymers, methacrylate polymers, fluorocarbonpolymers, and cycloaliphatic polymers such as norbornene-based andmaleic anhydride polymers. Some examples of specific polymers includepoly(3-hydroxystyrene), poly(acrylic acid), poly(norbonene carboxylicacid), copolymer of (4-hydroxystyrene and styrene), copolymer of4-hydroxystyrene and acrylic acid, copolymer of styrene and acrylicacid, and copolymer of norbonene and maleic anhydride.

The lithographic structures comprising the silicon and organicantireflective materials will likely exhibit excellent reflectivitycontrol in particular at 193 nm lithography with a numerical aperturegreater than 0.75 NA. Reflectivity control is accomplished by providingthe appropriate optical properties for each of the silicon and theorganic antireflective materials. The chromophore and organictransparent groups are optimized to achieve the appropriate index ofrefraction (both real and imaginary; n and k respectively) at 193 nm or157 nm wavelengths.

FIG. 1 shows a reflectivity simulation (software “Prolith” from KLA,Inc.) for a traditional, single antireflective material and for alithographic structure with an antireflective material that comprises asilicon antireflective material and an organic antireflective material.The substrate reflectivity of 193 nm radiation is plotted against theincident angle of the light. The angle is expressed as n*sin(θ), where θis the incident angle and n is the index of refraction of the imagingmedium. This value is also known as the numerical aperture of theimaging system. In this case, the imaging medium is considered to havean index of refraction of 1.43, which is the index of refraction ofwater at 193 nm. This value is chosen to be consistent with theindustry's choice of water as the imaging medium for immersionlithography, but the invention is not specific to any particular imagingmedium.

In general, the organic antireflective material will have an index ofrefraction (n) of 1.3-2.0 and an extinction coefficient (k) of 0.4-0.9,at 193 nm radiation, and the silicon antireflective material will havean index of refraction (n) of 1.5-2.2 and an extinction coefficient (k)of 0.1-0.8, at 193 nm radiation. Ideally, the antireflective materialsof the invention provide a semiconductor structure with a reflectivitybelow 0.5% up to NA=1.4, thus demonstrating excellent reflectivitycontrol for a high NA lithography imaging process.

The optical constants and thickness used for the traditionalantireflective material are n=1.8 and k=0.5 and a thickness of 30 nm.The optical constants and thickness used for the silicon and organicantireflective materials are n=1.75, k=0.2, thickness=35 nm and n=1.7,k=0.5, and thickness 200 nm, respectively. As shown, the traditionalmaterial reflectivity at low NA is adequate if below 1%. In general, itis desired to have an antireflective material structure that results inreflectivity below 1% of the incident light. However, at high NA (NA>1)the reflectivity increases sharply to values as high as 3-5%, which istypically considered unacceptable for a lithographic process. Incomparison, applicants' lithographic structure provides a reflectivitybelow 0.5% up to NA=1.4, thus demonstrating excellent reflectivitycontrol for a high NA lithography imaging process. It is to beunderstood, however, that it is not necessary to have the exact opticalconstants and thickness values shown in this example in order to attainlow reflectivity, and in fact these values will vary depending upon theunderlying film stack.

Table 1 provides a range of optical properties and thickness that mayresult in low reflectivity control depending upon the underlying filmstack. TABLE 1 structure material thickness (nm) n k photoresist n/a1.6-2.3   0-0.05 silicon 10-150 1.3-2.2   0-0.5 organic 20-500 1.3-2.20.2-1.0

The thickness of the silicon and organic antireflective materialsdepends upon the desired function. For most applications, the thicknessof the silicon antireflective material is typically about 20 nm to 100nm. To achieve complete planarization the desired film thickness of theorganic antireflective material is typically about 100 nm to 500 nm.Generally, the silicon antireflective material will have a thickness ofT_(k) (in nanometers) and the organic antireflective material will havea thickness of about 2T_(k) to about 12T_(k). In many instances, theorganic antireflective material will have a thickness of about 2T_(k) toabout 6T_(k).

The silicon and organic antireflective material is especiallyadvantageous for lithographic processes used in the manufacture ofintegrated circuits on semiconductor substrates. The lithographicstructure is especially advantageous for lithographic processes using193 nm, 157 nm, x-ray, e-beam or other imaging radiation. Thecomposition is also especially useful for 193 nm high NA lithographywith a numerical aperture (NA) ranging from 0.5-1.4.

The silicon and organic antireflective material can be used incombination with any desired photoresist material in the formation of alithographic semiconductor structure. Preferably, the photoresist can beimaged with low wavelength radiation or with electron beam radiation.Examples of suitable resist materials are U.S. Pat. No. 6,037,097, thedisclosure of which is incorporated herein by reference.

The invention is also directed to a process of making a semiconductorstructure comprising:

providing a substrate;

providing an organic antireflective material on the substrate;

providing a silicon antireflective material on the organicantireflective material, wherein the silicon antireflective materialcomprises a crosslinked polymer with a SiO_(x) backbone, a chromophoreattached to the SiO_(x) backbone; and an organic group that issubstantially transparent to 193 nm or 157 nm radiation,

-   -   depositing a photoresist on the silicon antireflective material,        pattern expose the photoresist to radiation, and remove portions        of the photoresist to expose the silicon antireflective        material,    -   removing portions of the silicon antireflective material to        expose the organic antireflective material;    -   removing portions of the organic antireflective material to        expose portions of the substrate; and    -   removing portions of the substrate Any remaining portions of the        photoresist, the silicon antireflective material, and the        organic antireflective material are then removed to provide a        patterned substrate.

An organic antireflective composition is applied, preferably byspin-coating, to a substrate, e.g., a dielectric or metal material, tobe patterned. The deposited organic, polymer composition is then heatedto remove solvent and cure (crosslink) the composition. The siliconpolymer composition is then applied to the organic antireflectivematerial by spin coating and cured. A radiation-sensitive resistmaterial can then be applied (directly or indirectly) on the siliconantireflective material.

Typically, the solvent-containing resist composition is applied usingspin coating or another technique. The photoresist coating is thentypically heated (pre-exposure baked) to remove the solvent and improvethe coherence of the photoresist material. The pre-exposure baketemperature may vary depending on the glass transition temperature ofthe photoresist. The thickness of the photoresist is preferably designedas thin as possible with the provisos that the thickness issubstantially uniform and that the photoresist material be sufficient towithstand subsequent processing (typically reactive ion etching) totransfer the lithographic pattern.

After solvent removal, the resist material is then patternwise-exposedto the desired radiation (e.g. 193 nm ultraviolet radiation). Wherescanning particle beams such as electron beam are used, patternwiseexposure can be achieved by scanning the beam across the substrate andselectively applying the beam in the desired pattern. If ultravioletradiation is used, the patternwise exposure is conducted through a maskwhich is placed over the resist material. For 193 nm UV radiation, thetotal exposure energy is about 100 millijoules/cm² or less, or about 50millijoules/cm² or less (e.g. 15-30 millijoules/cm²).

After the desired patternwise exposure, the resist material is typicallybaked to further complete the acid-catalyzed reaction and to enhance thecontrast of the exposed pattern. The post-exposure bake is preferablyconducted at about 60° C.-175° C., more preferably about 90° C.-160° C.The post-exposure bake is preferably conducted for about 30 seconds to 5minutes. After post-exposure bake, the photoresist with the desiredpattern is developed by contacting the resist material with an alkalinesolution which selectively dissolves the areas of the resist which wereexposed to the radiation. Preferred alkaline solutions (developers) areaqueous solutions of tetramethyl ammonium hydroxide. The resultinglithographic structure on the substrate is then typically dried toremove any remaining developer solvent.

In some cases it maybe desirable to remove the resist selectively to thesilicon antireflective material as part of a rework process in case ofmissprocessing of the resist during the lithographic process. Theremoval of the resist can be accomplished by dissolving the resist in anorganic solvent, followed by baking to remove the solvent and theresist. Any solvent dissolving a photoresist is suitable. In some casesit is desirable to use solvents containing bases such as tetramethylammonium hydroxide or aqueous based solutions containing ammoniumhydroxide. In some cases it is desirable to remove the siliconantireflective material and the photoresist selectively to the organicantireflective material. In this case the solution for removal of thephotoresist can contain fluorine. Alternatively, it is possible to etchthe resist and/or the silicon antireflective material by a dry stripusing a plasma containing fluorine, carbon, hydrogen, chlorine, oxygen,bromine, nitrogen, sulfur and/or mixtures thereof. Of course, acombination of two described methods can also be used.

On advantage provided by the silicon and organic antireflective materialis that by optimizing the RIE condition using a reactive ion plasmaconsisting of C, F, H, N, S O and mixtures thereof, excellentselectivity between the silicon and organic antireflective materials canensure good pattern transfer. Once the organic antireflective materialis patterned, the selective removal of the underlying substrate, e.g., adielectric, can continue since there is sufficient organic material leftfor all subsequent etch steps.

In one embodiment, the proper pattern transfer based on the etchselectivity between photoresist, silicon antireflective material andorganic antireflective material is exemplified in FIG. 2. By using afluorocarbon plasma, e.g., CF₄/O₂, a reactive ion etch (RIE) process,pattern transfer from the photoresist 10 into the silicon antireflectivematerial 12 is established without consuming much of the photoresist.The high etch selectivity in combination with choosing the appropriatethickness for the silicon antireflective material enables the use ofrelatively thin photoresists. The pattern is then transferred into theunderlying organic antireflective material 14. By using anon-fluorocarbon plasma based RIE process good selectivity between thesilicon antireflective material and organic antireflective material isestablished as well as consumption of the photo resist. Once the organicantireflective material is patterned, the pattern is then transferred tothe substrate 16. If the substrate is a dielectric material such as anoxide or low k silicon based dielectrics, then a fluorocarbon based RIEprocess will likely ensure consumption of the silicon antireflectivematerial as well as good selectivity between the organic material andthe dielectric. The remaining organic antireflective material is thenremoved by methods known to those in the art.

The lithographic structure can also be used to introduce a taper duringthe etch of the organic antireflective material, which effectively leadsto reduction in bottom critical dimension compared to the bottomcritical dimension after lithography of contact hole patterning.Introducing a taper during etch of contact holes using theantireflective structure provides an effective shrink method especiallyfor contact hole pattern. Ion sputtering can be used to taper the corneredges of the organic antireflective material.

The lithographic structure can be used to create patterned materialstructures such as metal wiring lines, holes for contacts or vies,insulation sections (e.g., damascene trenches or shallow trenchisolation), trenches for capacitor structures, etc, as might be used inthe design of integrated circuit devices. The lithographic structure isespecially useful in the context of creating patterned materials ofsubstrates such as oxides, nitrides or polysilicon.

Examples of general lithographic processes where the lithographicstructure can be useful are disclosed in U.S. Pat. Nos. 4,855,017;5,362,663; 5,429,710; 5,552,801; 5,618,751; 5,744,376; 5,801,094;5,821,469 and 5,948,570. Other examples of pattern transfer processesare described in Chapters 12 and 25 of “Semiconductor Lithography,Principles, Practices, and Materials” by Wayne Moreau, Plenum Press,(1988), the disclosure of which is incorporated herein by reference. Itshould be understood that the invention is not limited to any specificlithographic technique or device structure.

EXAMPLE 1 Silicon and Organic Antireflective Materials Deposited by SpinCoating

The organic polymer composition, NFC-1400, commercially available fromJSR Microelectronics was spin coated onto an oxide wafer at 3995 rpm andbaked at 170° C. for 60 sec providing an organic antireflective materialof a thickness of 200 nm and the optical constants of n=1.7 and k=0.8 k(193 nm). The silicon polymer composition, SHBA470, available fromShin-Etsu Chemical, was spin coated onto the organic antireflectivematerial at 3000 rpm and baked at 200° C. for 120 sec providing asilicon antireflective material with a thickness of 20 to 35 nm andoptical constants of n=1.85 and k=0.2 (193 nm).

EXAMPLE 2 193 nm Lithography and Etching the Antireflective Materials

The antireflective materials were formed as described in Example 1. Amaterial of acrylic-based photoresist (available from JSRMicroelectronics and Shin-Etsu) was spin-coated over the siliconantireflective material to a thickness of about 250 nm. The photoresistwas baked at 130° C. for 60 sec. The photoresist was imaged using a 0.75NA ASML Stepper with conventional and annular illumination using a APSMreticle. After patternwise exposure, the photoresist was baked at 130°C. for 60 sec. The image was then developed using commercial developer(0.26M TMAH). The resulting pattern showed 90 nm lines with differentpitches as well as isolated and nested 120 nm contact holes.

EXAMPLE 3

The photoresist of Example 2 was selectively removed to SHB A470 on topof NFC-1400 (Example 1) by applying a solvent mixture of y-butyrolactoneand butylacetate after patterning. Then the photoresist was reapplied(the wafer was spun at 3000 rpm for 30 sec followed by a bake of 130° C.for 30 sec) and exposed as described in Example 2 to give lines andspaces pattern that were in size and profile identical to the patternsobtained on SHBA470 and NFC 1400 (Example 1) without solvent rinse

The pattern (lines and spaces as well as contact holes) were thentransferred into the silicon material (Example 1) by a fluorocarbonplasma using a LAM RIE tool. The etch selectivity between thephotoresist and the silicon antireflective material exceeded 3:1demonstrating that little consumption of photoresist is lost during thesilicon antireflective material open etch. The pattern was transferredby a nitrogen hydrogen based etch into the organic antireflectivematerial. During this step the photoresist was almost completelyconsumed, however, the silicon antireflective material showed nosignificant degradation. The pattern was transferred into a material of300 nm oxide by a fluorocarbon plasma RIE process, which completelyconsumes the silicon antireflective material. The remaining organicantireflective material was stripped by a nitrogen, hydrogen etch.

EXAMPLE 4 Shrink by Etch

After etching through the antireflective materials (Example 1, SHBA470and NFC1400) using CF based RIE chemistry for the silicon antireflectivematerial and nitrogen hydrogen based RIE chemistry for the organicantireflective material, a reduction of bottom critical dimension of15-20 nm was observed in the contact hole patterned in Example 2indicating that the antireflective structure can be used as an effectivecontact shrink method via RIE.

1. A lithographic structure comprising: an organic antireflectivematerial disposed on a substrate; and a silicon antireflective materialdisposed on the organic antireflective material, wherein the siliconantireflective material comprises a crosslinked polymer with a SiO_(x)backbone, a chromophore attached to the SiO_(x) backbone, and atransparent organic group that is substantially transparent to 193 nm or157 nm radiation.
 2. The lithographic structure of claim 1 wherein thechromophore provides the site for crosslinking.
 3. The lithographicstructure of claim 1 wherein the chromophore is selected from the groupconsisting of phenyl, phenol, naphthalene, and an unsaturated organicgroup.
 4. The lithographic structure of claim 1 wherein the crosslinkedpolymer further comprises a reaction product resulting from the reactionof a thermal acid generator.
 5. The lithographic structure of claim 1wherein the transparent organic group that is substantially transparentprovides the site of crosslinking.
 6. The lithographic structure ofclaim 1 wherein the transparent organic group is a hydrofluorocarbon orperfluorocarbon.
 7. The lithographic structure of claim 5 wherein thetransparent organic group includes one or more organic functional groupselected from an epoxide, alcohol, acetoxy, ester or ether.
 8. Thelithographic structure of claim 5 wherein the transparent organic groupis a cycloaliphatic epoxide.
 9. The lithographic structure of claim 1wherein the crosslinked polymer comprises units of a glycolurilcompound.
 10. The lithographic structure of claim 1 wherein the organicantireflective material comprises a polymer with crosslinked phenolicsites, and a number average molecular weight of about 2,000 to about10,000.
 11. The lithographic structure of claim 1 further comprising aphotoresist on the silicon antireflective material.
 12. The lithographicstructure of claim 1 wherein the organic antireflective material has anindex of refraction (n) of 1.3-2.0 and an extinction coefficient (k) of0.4-0.9, at 193 nm radiation, and the silicon antireflective materialhas an index of refraction (n) of 1.5-2.2 and an extinction coefficient(k) of 0.1-0.8 at 193 nm radiation.
 13. The lithographic structure ofclaim 1 wherein the silicon antireflective material and the organicantireflective material together provide a reflectivity below 0.5% up tonumerical aperture (NA) of 1.4.
 14. The lithographic structure of claim4 wherein the silicon antireflective material and the organicantireflective material together provide a reflectivity below 0.5% up tonumerical aperture (NA) of 1.4.
 15. The lithographic structure of claim7 wherein the silicon antireflective material and the organicantireflective material together provide a reflectivity below 0.5% up tonumerical aperture (NA) of 1.4.
 16. The lithographic structure of claim1 wherein the silicon antireflective material has a thickness of T_(k)and the organic antireflective material has a thickness of about 2T_(k)to about 12T_(k), wherein the thickness T_(k) is in nanometers.
 17. Anantireflective material comprising an organic antireflective materialand a silicon antireflective material disposed on the organicantireflective material, wherein the silicon antireflective materialcomprises: a crosslinked polymer with a SiO_(x) backbone; a chromophoreattached to the SiO_(x) backbone; and a transparent organic group thatis substantially transparent to 193 nm or 157 nm radiation.
 18. Theantireflective material of claim 17 wherein the silicon antireflectivematerial further comprises a reaction product resulting from thereaction of a thermal acid generator.
 19. The antireflective material ofclaim 17 wherein the transparent organic group provides the site ofcrosslinking, and is one or more organic functional groups selected froman epoxide, alcohol, acetoxy, ester or ether.
 20. The antireflectivematerial 19 wherein the transparent organic group is a cycloaliphaticepoxide.
 21. The antireflective material of claim 17 wherein the organicantireflective material has an index of refraction (n) of 1.3-2.0 and anextinction coefficient (k) of 0.4-0.9, at 193 nm radiation, and thesilicon antireflective material has an index of refraction (n) of1.5-2.2 and an extinction coefficient (k) of 0.1-0.8 at 193 nmradiation, and the silicon antireflective material and the organicantireflective material together provide a reflectivity below 0.5% up tonumerical aperture (NA) of 1.4.
 22. The antireflective material of claim17 wherein the silicon antireflective material has a thickness of T_(k)and the organic antireflective material has a thickness of about 2T_(k)to about 12T_(k), wherein the thickness T_(k) is in nanometers.
 23. Aprocess of making a lithographic structure comprising: providing asubstrate; providing an organic antireflective material on thesubstrate; providing a silicon antireflective material on the organicantireflective material, wherein the silicon antireflective materialcomprises a crosslinked polymer with a SiO_(x) backbone, a chromophoreattached to the SiO_(x) backbone; and a transparent organic group thatis substantially transparent to 193 nm or 157 nm radiation, depositing aphotoresist on the silicon antireflective material, pattern expose thephotoresist to radiation, and remove portions of the photoresist toexpose the silicon antireflective material, removing portions of thesilicon antireflective material to expose the organic antireflectivematerial; removing portions of the organic antireflective material toexpose portions of the substrate; and removing portions of thesubstrate.
 24. The process of claim 23 wherein removing portions of thesilicon antireflective material, and the organic antireflective materialis accomplished by reactive ion etching in a plasma.
 25. The process ofclaim 23 wherein the deposited silicon antireflective material has athickness T_(k) and the organic antireflective material has a thicknessof about 2T_(k) to about 12T_(k), wherein the thickness T_(k) is innanometers.
 26. The process of claim 23 wherein the deposited siliconantireflective material and the deposited organic antireflectivematerial together provide a reflectivity below 0.5% up to numericalaperture (NA) of 1.4.
 27. The process of claim 24 wherein the siliconantireflective material further comprises a reaction product resultingfrom the reaction of a thermal acid generator.
 28. The process of claim24 wherein the removing portions of the organic antireflective materialincludes introducing a taper.
 29. A process of claim 23 wherein thesilicon antireflective material comprises the silicon backbone of

which is crosslinked with a crosslinking agent of formula

and prepared in the presence of an acid generator of formula

wherein A is S or I, and x is 0 to 7.